Some ideas after spending on it about 5 min—but may be useful somehow
Oklo was a natural fission reactor, Wikipedia states that it stayed isolated for 2 billion years. In general research on long-term storage of nuclear waste is on shorter timescales may contain some insights
civilization ca 1900 may be curious about some rare elements, minerals, high concentrations of uranium, or similar. some of the current deposits may be transformed, buried deep etc, but enough of them may end up close to surface to be economic to exploit even after long time.
magnetic anomalies are something civilization notices early, and would largest anomalies may be stable on timescales of billions of years. pointers like “search close to the centre of the largest magnetic anomaly” may work
I explored the use of the Earth-based data storages in my article about preservation data on the Moon:
Below is the section from the article which was cut from the final version, where I explore the terrestrial places for long term preservation:
6. Other possible solutions for information preservation
6.1. Cratons on Earth and beacons in them created using cavities
The most stable places on Earth’s surface are cratons, some of them include very old rock with age 3-4 billion years. These pieces of crust were not recycled by plate tectonics, as they have higher buoyancy. Scientists will probably be able to calculate which part of Earth will remain on the surface for the next billion years, and most probably it will be the same old cratons. Based on resent models, the age of cratons is ending (Cooper & Conrad, 2009), as mantle viscosity grows and increases convection stress. However, we assume that some cratons may exist for the next several hundred million years or more.
The oldest rocks will attract attention of future scientists. But if a hole is drilled in a large crystal massif and a small disk is placed inside, it will probably never be found. So the main problem would be creating a beacon, which will show where the message is located. Remnants of underground nuclear explosions inside a crystal shield may play the same role as crater drawings on the Moon. Another option to create a beacon is use the gradient of a rare element interesting for future scientists to point to the direction of the message.
A large project exists of geological storage of radioactive waste at 420 m depth in a granite shield: Onkalo project in Finland (Black, 2006). Burial places are selected to be very stable (but may be not the best in the world because of social factors) Rare materials and radioactivity from the storages could be used as a beacon, the same way as isotopic changes helped to identify natural uranium nuclear fission reactor in Gabon, which remained in place for 2 bln years (Gauthier-Lafaye, Holliger, & Blanc, 1996). If empty tunnels are filled with concrete after the project is finished, they may remain their structure for a very long time.
If the data were placed in the Onkalo hole, there will be zero expenditures on construction, and positive PR for the project by data preservation, so it could be funded from its advertisement budgets. It expected to provide protection for at least 100 000 years and able to survive weight of a new glacier during next Ice age. Steel containers are designed to withstand pressure even if the rock wall collapses. The price of the project is around 5 billion USD (“Finland to bury nuclear waste in tomb for 100,000 years,” 2016). The main problem is to make future archeologists interested in excavating the tunnels. Many copies of the messages may be placed in the different places of the tunnels for a small percent of the total project.
Another nuclear waste management project is drilling a 5 km borehole in North Dakota, U.S. in crystalline rock.
The fact that scientists have found large skeletons of dinosaurs, or early insects’ imprints inside rock, demonstrate that information can be sent on Earth hundreds of millions of years into the future. If the message is imprinted in solid stone, it could survive geological epochs.
I’m not very clear on the underlying geology here. Are there points on the earth where a large beacon deposited on the surface would have a chance of remaining on the surface for hundreds of millions of years?
In short: Beacon unlikely to survie on the surface, but the structure of underground tunnels could be visible via seismic measurements, or a gradient of rare elements. For example, tunnels could be put in such order that they form something like diffraction grid for typical seismic waves and this unusual deflection of the waves will be visible for the future scientist. However, I think that creation of the beacon on the Moon surface is more feasible via ditching lines.
More detailed: We have 4 billions years old rock formations in Australia, and micrometer size fossils of early microorganisms survived for billions of years which imply possibility of sending data in the future. We could also predict which rock will likely not disappear in the next hundreds millions of years. So if we put an object deep into such rock, it will survive for very long time and could carry information onto the future.
There is also a data preservation project in a salt mine in Austria, but they are going to send data 1 million years in future only using printing on ceramic plates, and many small maps printed on ceramic coins as beacons. https://en.wikipedia.org/wiki/Memory_of_Mankind
The main problem of leaving long-term data storages on Earth is beacons, not data. However, I found a possible solution: use large underground storages of radioactive materials as possible storage locations and beacons. The reasons:
1) The are already in the rock which is proved to survive for long-term, like Scandinavian crystal shield.
2) They are deep undersurface, so surface scratching by future ice ages etc will not affect them.
3) Such storage is a large structure of artificial form, which could be found via some advance seismic measurements.
4) Radiological waste storage consists of the system of horizontal tunnels which could be planned as a drawing, so its plan could be part of the message, like a spiral, which centered in the place of location of the main message, or even as a diffraction grid or a hologram, which change direction of the seismic waves in a very peculiar way. However, the Finish project is already built, so using tunnels for drawing is not possible here.
5) The whole project could have negative cost, as radiological waste storages have bad PR and large sunk cost, so using them for ensuring human survival could be done as part of their PR project. It will cost only small fraction of the radiological storage which costs 3 bn.
Use the Kursk Magnetic Anomaly. It is apparently easy to notice (humanity noticed it as early as 1773!) and is interesting for any future technical civilization for practical purposes, as it is one of the most massive iron ore basins on the planet (some sources claim it is about 50% of the surface iron ore reserves). So they will start digging.
Apart from that, it has the advantage of being part of the east-european craton, so it has higher chances to survive plate tectonics.
Anything directly on the surface will still get destroyed by glaciation, but there are huge iron ore mines at the area, which may leave some traces, and grab some attention.
There are also big underground mines.
So, here is somewhat practical proposal: put big blocks of neodymium-iron magnets in some of the possible more noticeable places of KMA, like centres of the largest mines, places of the strongest magnetic anomaly, or places with the largest not-yet-mined Fe deposits. Bury them somewhat. These could work as beacons, and are likely to be noticed by magnetic measurements (which are likely to be conducted either to determine where to dig for iron, or out of scientific curiosity) or when digging iron ore.
(information would be inside of the huge iron blocks, so they would work also as a shield)
Burry the message also in KMA in some of the deep mines, and give coordinates to it relative to the beacons. These will work regardless of big plate movements.
How large a magnet would you need to be noticeable at a reasonable distance? (E.g. how large a magnet would you need for us to have noticed it at a depth of 30 feet or whatever?)
How expensive is the cheapest magnet of that size, and will they last 500M years?
Intuitively, I wouldn’t expect that you can use magnets to significantly increase the visibility of the beacon.
Somewhat more precise estimate, with magnetite, as it is apparently the cheapest material (more on that later).
The mineral magnetite has a volume magnetic susceptibility ca 1x10^6 − 5.6x10^6 (roughly, that is the ratio of the created field compared to the “background” field.
In far regions, the magnetic field of a sphere with radius $a$ behaves as magnetic dipole with moment $ m = 4⁄3 \Pi a^3 M $, where magnetization M is roughly external field x susceptibility.
Dipole field decays (the important quantity being “magnetic flux density”) in the leading order approximation as $ \mu / (4Pi) m r^-3 $
So, a 1m magnetite sphere will create larger than 10% disturbance in the external field as far as 100m away. Earth’s surface magnetic field strength is between 0.25x10^-6 and 0.65x10^-6 Tesla, fluxgate magnetometers discovered in ca 1936 have precision of order 10^-8 Tesla.
So by this simple account, something which can be noticed by surface magnetic measurements is not that difficult to construct. As I see it now, the bigger problem is creating field disturbance “strange enough” that it will be noticed as something not natural, in comparison to the natural background. There is huge amount of magnetite in the area.… E.g. straight lines of material are bad, as there is a lot of magnetite deposits of this kind.
Also the limiting factor is probably not the depth of burial, but the spacing of the measurement grid—according to this source, “Magnetic surveys are usually made with magnetometers borne by aircraft flying in parallel lines spaced two to four kilometers apart at an elevation of about 500 metros when exploring for petroleum deposits and in lines 0.5 to one kilometer apart roughly 200 metros above the ground when searching for mineral concentrations. Ground surveys are conducted to follow up magnetic anomaly discoveries made from the air. Such surveys may involve stations spaced only 50 meters apart. ”
To get to the practical proposal.
KMA is so big that it is easily measurable from space, or noticeable by relatively primitive technology. It seems likely that it would be interesting for any technical civilization looking for sources of iron. It also seems likely such civilization would do higher resolution survey with lines spaced between hundreds of meters to ~ kms, as it is the way how to find the highest mineral concentrations.
The question is what would be noticeable pattern. My first guess is that rather than create something completely new, it may be better to use the largest existing open pit mines, or deposits of waste material. I’ll try asking some geologist how strange would these look in future magnetic surveys, when buried. Than the next step could be 1] trying to shape the mine or the deposit so it looks more un-natural 2] creating some higher resolution structure, such as big cube of magnetite in the waste deposit 3] create some non-magnetic beacon in the area
The advantage may be that 1] and 2] may basically mean moving some materials withing an existing mine. How much does it cost is a bit unclear, in practice would depend on negotiations with a mining company in Russia.
(some caveats of the whole proposal are that the whole area at some unknown point in the future may be glaciated, or turned into a desert, or have some other property making it unattractive for exploration)
Also it may be worth looking into other types of mining efforts as a place for beacons: the general pattern is technical civilizations will be looking for some raw minerals, so the largest deposits are something like “Shelling points”. And at the same times mines & waste deposits are some of the largest “structures” humanity creates.
I’ll do a more precise calculation in a day or two, but magnetic materials are noticeable when buried. The intuitive reason is the spins in ferromagnetic materials align themselves with the external field, increasing the field inside the magnet so strongly, that it changes earths field noticeably even at somewhat large distances, and even when buried.
The thing to optimize for is likely something like field change when buried of an object large enough to be visible on some realistic grid size, per dollar.
As a quick guess, something like a spiral or other shape 1km wide made from ferite magnet 1x1m cross-section would have been noticed by a survey using WW2 instruments when buried 10m deep, in an area where some survey was done.
Some ideas after spending on it about 5 min—but may be useful somehow
Oklo was a natural fission reactor, Wikipedia states that it stayed isolated for 2 billion years. In general research on long-term storage of nuclear waste is on shorter timescales may contain some insights
civilization ca 1900 may be curious about some rare elements, minerals, high concentrations of uranium, or similar. some of the current deposits may be transformed, buried deep etc, but enough of them may end up close to surface to be economic to exploit even after long time.
magnetic anomalies are something civilization notices early, and would largest anomalies may be stable on timescales of billions of years. pointers like “search close to the centre of the largest magnetic anomaly” may work
(I limited myself to terrestrial objects)
I explored the use of the Earth-based data storages in my article about preservation data on the Moon:
Below is the section from the article which was cut from the final version, where I explore the terrestrial places for long term preservation:
6. Other possible solutions for information preservation
6.1. Cratons on Earth and beacons in them created using cavities
The most stable places on Earth’s surface are cratons, some of them include very old rock with age 3-4 billion years. These pieces of crust were not recycled by plate tectonics, as they have higher buoyancy. Scientists will probably be able to calculate which part of Earth will remain on the surface for the next billion years, and most probably it will be the same old cratons. Based on resent models, the age of cratons is ending (Cooper & Conrad, 2009), as mantle viscosity grows and increases convection stress. However, we assume that some cratons may exist for the next several hundred million years or more.
The oldest rocks will attract attention of future scientists. But if a hole is drilled in a large crystal massif and a small disk is placed inside, it will probably never be found. So the main problem would be creating a beacon, which will show where the message is located. Remnants of underground nuclear explosions inside a crystal shield may play the same role as crater drawings on the Moon. Another option to create a beacon is use the gradient of a rare element interesting for future scientists to point to the direction of the message.
A large project exists of geological storage of radioactive waste at 420 m depth in a granite shield: Onkalo project in Finland (Black, 2006). Burial places are selected to be very stable (but may be not the best in the world because of social factors) Rare materials and radioactivity from the storages could be used as a beacon, the same way as isotopic changes helped to identify natural uranium nuclear fission reactor in Gabon, which remained in place for 2 bln years (Gauthier-Lafaye, Holliger, & Blanc, 1996). If empty tunnels are filled with concrete after the project is finished, they may remain their structure for a very long time.
If the data were placed in the Onkalo hole, there will be zero expenditures on construction, and positive PR for the project by data preservation, so it could be funded from its advertisement budgets. It expected to provide protection for at least 100 000 years and able to survive weight of a new glacier during next Ice age. Steel containers are designed to withstand pressure even if the rock wall collapses. The price of the project is around 5 billion USD (“Finland to bury nuclear waste in tomb for 100,000 years,” 2016). The main problem is to make future archeologists interested in excavating the tunnels. Many copies of the messages may be placed in the different places of the tunnels for a small percent of the total project.
Another nuclear waste management project is drilling a 5 km borehole in North Dakota, U.S. in crystalline rock.
The fact that scientists have found large skeletons of dinosaurs, or early insects’ imprints inside rock, demonstrate that information can be sent on Earth hundreds of millions of years into the future. If the message is imprinted in solid stone, it could survive geological epochs.
I’m not very clear on the underlying geology here. Are there points on the earth where a large beacon deposited on the surface would have a chance of remaining on the surface for hundreds of millions of years?
In short: Beacon unlikely to survie on the surface, but the structure of underground tunnels could be visible via seismic measurements, or a gradient of rare elements. For example, tunnels could be put in such order that they form something like diffraction grid for typical seismic waves and this unusual deflection of the waves will be visible for the future scientist. However, I think that creation of the beacon on the Moon surface is more feasible via ditching lines.
More detailed: We have 4 billions years old rock formations in Australia, and micrometer size fossils of early microorganisms survived for billions of years which imply possibility of sending data in the future. We could also predict which rock will likely not disappear in the next hundreds millions of years. So if we put an object deep into such rock, it will survive for very long time and could carry information onto the future.
There is also a data preservation project in a salt mine in Austria, but they are going to send data 1 million years in future only using printing on ceramic plates, and many small maps printed on ceramic coins as beacons. https://en.wikipedia.org/wiki/Memory_of_Mankind
The main problem of leaving long-term data storages on Earth is beacons, not data. However, I found a possible solution: use large underground storages of radioactive materials as possible storage locations and beacons. The reasons:
1) The are already in the rock which is proved to survive for long-term, like Scandinavian crystal shield.
2) They are deep undersurface, so surface scratching by future ice ages etc will not affect them.
3) Such storage is a large structure of artificial form, which could be found via some advance seismic measurements.
4) Radiological waste storage consists of the system of horizontal tunnels which could be planned as a drawing, so its plan could be part of the message, like a spiral, which centered in the place of location of the main message, or even as a diffraction grid or a hologram, which change direction of the seismic waves in a very peculiar way. However, the Finish project is already built, so using tunnels for drawing is not possible here.
5) The whole project could have negative cost, as radiological waste storages have bad PR and large sunk cost, so using them for ensuring human survival could be done as part of their PR project. It will cost only small fraction of the radiological storage which costs 3 bn.
Nice.
So a more specific proposal:
Use the Kursk Magnetic Anomaly. It is apparently easy to notice (humanity noticed it as early as 1773!) and is interesting for any future technical civilization for practical purposes, as it is one of the most massive iron ore basins on the planet (some sources claim it is about 50% of the surface iron ore reserves). So they will start digging.
Apart from that, it has the advantage of being part of the east-european craton, so it has higher chances to survive plate tectonics.
Anything directly on the surface will still get destroyed by glaciation, but there are huge iron ore mines at the area, which may leave some traces, and grab some attention.
There are also big underground mines.
So, here is somewhat practical proposal: put big blocks of neodymium-iron magnets in some of the possible more noticeable places of KMA, like centres of the largest mines, places of the strongest magnetic anomaly, or places with the largest not-yet-mined Fe deposits. Bury them somewhat. These could work as beacons, and are likely to be noticed by magnetic measurements (which are likely to be conducted either to determine where to dig for iron, or out of scientific curiosity) or when digging iron ore.
(information would be inside of the huge iron blocks, so they would work also as a shield)
Burry the message also in KMA in some of the deep mines, and give coordinates to it relative to the beacons. These will work regardless of big plate movements.
How large a magnet would you need to be noticeable at a reasonable distance? (E.g. how large a magnet would you need for us to have noticed it at a depth of 30 feet or whatever?)
How expensive is the cheapest magnet of that size, and will they last 500M years?
Intuitively, I wouldn’t expect that you can use magnets to significantly increase the visibility of the beacon.
Somewhat more precise estimate, with magnetite, as it is apparently the cheapest material (more on that later).
The mineral magnetite has a volume magnetic susceptibility ca 1x10^6 − 5.6x10^6 (roughly, that is the ratio of the created field compared to the “background” field.
In far regions, the magnetic field of a sphere with radius $a$ behaves as magnetic dipole with moment $ m = 4⁄3 \Pi a^3 M $, where magnetization M is roughly external field x susceptibility.
Dipole field decays (the important quantity being “magnetic flux density”) in the leading order approximation as $ \mu / (4Pi) m r^-3 $
So, a 1m magnetite sphere will create larger than 10% disturbance in the external field as far as 100m away. Earth’s surface magnetic field strength is between 0.25x10^-6 and 0.65x10^-6 Tesla, fluxgate magnetometers discovered in ca 1936 have precision of order 10^-8 Tesla.
So by this simple account, something which can be noticed by surface magnetic measurements is not that difficult to construct. As I see it now, the bigger problem is creating field disturbance “strange enough” that it will be noticed as something not natural, in comparison to the natural background. There is huge amount of magnetite in the area.… E.g. straight lines of material are bad, as there is a lot of magnetite deposits of this kind.
Also the limiting factor is probably not the depth of burial, but the spacing of the measurement grid—according to this source, “Magnetic surveys are usually made with magnetometers borne by aircraft flying in parallel lines spaced two to four kilometers apart at an elevation of about 500 metros when exploring for petroleum deposits and in lines 0.5 to one kilometer apart roughly 200 metros above the ground when searching for mineral concentrations. Ground surveys are conducted to follow up magnetic anomaly discoveries made from the air. Such surveys may involve stations spaced only 50 meters apart. ”
To get to the practical proposal.
KMA is so big that it is easily measurable from space, or noticeable by relatively primitive technology. It seems likely that it would be interesting for any technical civilization looking for sources of iron. It also seems likely such civilization would do higher resolution survey with lines spaced between hundreds of meters to ~ kms, as it is the way how to find the highest mineral concentrations.
The question is what would be noticeable pattern. My first guess is that rather than create something completely new, it may be better to use the largest existing open pit mines, or deposits of waste material. I’ll try asking some geologist how strange would these look in future magnetic surveys, when buried. Than the next step could be 1] trying to shape the mine or the deposit so it looks more un-natural 2] creating some higher resolution structure, such as big cube of magnetite in the waste deposit 3] create some non-magnetic beacon in the area
The advantage may be that 1] and 2] may basically mean moving some materials withing an existing mine. How much does it cost is a bit unclear, in practice would depend on negotiations with a mining company in Russia.
(some caveats of the whole proposal are that the whole area at some unknown point in the future may be glaciated, or turned into a desert, or have some other property making it unattractive for exploration)
Also it may be worth looking into other types of mining efforts as a place for beacons: the general pattern is technical civilizations will be looking for some raw minerals, so the largest deposits are something like “Shelling points”. And at the same times mines & waste deposits are some of the largest “structures” humanity creates.
I’ll do a more precise calculation in a day or two, but magnetic materials are noticeable when buried. The intuitive reason is the spins in ferromagnetic materials align themselves with the external field, increasing the field inside the magnet so strongly, that it changes earths field noticeably even at somewhat large distances, and even when buried.
The thing to optimize for is likely something like field change when buried of an object large enough to be visible on some realistic grid size, per dollar.
As a quick guess, something like a spiral or other shape 1km wide made from ferite magnet 1x1m cross-section would have been noticed by a survey using WW2 instruments when buried 10m deep, in an area where some survey was done.
Excellent idea about KMA. However, needed Niodim magnets should be to be very large and expensive